The present invention pertains to the art of support devices for the human spine, more particularly to a trunk supporting exoskeleton configured to reduce the bending moment on a person's back during a forward bend.
In general, back support devices that are configured to assist a person in bending, lifting, or standing upright, or any combination of these, are known in the art. For example, see U.S. Pat. Nos. 6,436,065, 5,951,591, 5,176,622, and 7,744,552. U.S. Pat. Nos. 1,409,326 and 4,829,989 describe devices where moment is created during a bend to counteract the moments from a person's trunk gravity weight. These systems utilize a passive, spring resistance to create a torque between the wearer's torso and legs. By creating a restorative moment at the hip, the probability of injury of the L5/S1 area of the spine is greatly reduced. Once the angle between torso and leg reaches a predetermined angle during stooping, squatting, or walking, the devices provide resistance; however, none of the devices differentiates between walking and bending or sitting and bending. This means the user cannot walk comfortably using these passive devices since the user's legs must push against the devices during walking. Similarly, the user cannot sit comfortably using these passive devices since the user's legs must push against the devices during sitting. This is uncomfortable and hazardous, preventing the user from moving around unrestricted, and is the most important reason to avoid the use of these systems in various industrial settings. Unlike the aforementioned devices, the technology described here differentiates between walking and bending and between sitting and bending. Even though the relative angle between the user's trunk and a swinging thigh is similar to each other in both cases of bending and walking (or bending and sitting), we have discovered a means by which they can be distinguished using minimal sensing and hardware.